package com.leyou.item.service.impl;

import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.leyou.common.entity.Category;
import com.leyou.item.dto.CategoryDTO;
import com.leyou.item.entity.CategoryBrand;
import com.leyou.item.mapper.CategoryMapper;
import com.leyou.item.service.CategoryBrandService;
import com.leyou.item.service.CategoryService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;


@Service
public class CategoryServiceImpl extends ServiceImpl<CategoryMapper, Category> implements CategoryService {

    //先创建categoryBrandService对象并且注入
    private final CategoryBrandService categoryBrandService;

    @Autowired
    public CategoryServiceImpl(CategoryBrandService categoryBrandService) {
        this.categoryBrandService = categoryBrandService;
    }
    @Override
    public List<CategoryDTO> queryCategoryByBrandId(Long brandId) {
        // 1.根据品牌id，查询中间表，得到中间表对象集合
        List<CategoryBrand> categoryBrandList = categoryBrandService.query()
                .eq("brand_id", brandId).list();
        //判断是否为null，为空则返回一个新的list
        if(CollectionUtils.isEmpty(categoryBrandList)){
            return Collections.emptyList();
        }
        // 2.获取分类id集合
        //获取中间表的流，获取每个对象的CategoryId，收集获取到的id到list列表中.
        List<Long> categoryIdList = categoryBrandList.stream()
                .map(CategoryBrand::getCategoryId).collect(Collectors.toList());
        // 3.根据分类id集合，查询分类对象集合
        List<Category> categories = listByIds(categoryIdList);
        // 4.将查出来的list集合转换DTO类型的list
        return CategoryDTO.convertEntityList(categories);
    }
}